This invention relates to an imaging bar which includes an array of photosensitive reading elements and an array of associated marking elements, one for each reading element. All of the reading elements, marking elements, and circuits are carried as an integrated structure.
An image bar comprises a linear array of photosensors, such as photoresistors, coupled electrically to a parallel array of marking elements, such as styli. All of the sets of photosensors and marking elements, together with their associated coupling circuits, operate individually, simultaneously, in parallel. A device of this kind may be used as a copier element by exposing the photosensor array to an illuminated line image of an original, and by scanning with either the image or with the image bar to provide a line-by-line scan of an original document. The ouput side of the image bar may simultaneously write a line-by-line charge image on to a suitable receptor or recording medium to either cause direct coloration in correspondence with the original document or to provide a latent image of the original document for subsequent development.
An example of an image bar of this kind, employed as a copier element, is disclosed in U.S. Pat. No. 3,409,899 to Cowan et al and suggested in FIG. 6 of U.S. Pat. No. 4,257,071 to Lamb. Also, Pat. No. 4,271,435 to Takenouchi et al discloses a readout head that includes a combined array of lenses and aligned photosensitive elements to read an original document.
Cowan et al discloses an image bar comprising an array of photoresponsive elements comprising cadmium sulfide, deposited on one end of a support or substrate and an array of writing stylus deposited at the other end of the support with a voltage divider circuit arrangement for electrically coupling the photoresponsive elements and the writing stylus. The voltage supply, photoresponsive elements and the circuit arrangement are all operated at high voltages, e.g., above 200 volts, and provide high voltage directly to the sytlus for writing.
The problem with such an image bar is basically two fold. First, the photosensitive materials, employed, e.g., cadmium sulfide, require high levels of illumination for practical copying purposes and the levels of illumination required are much larger than those presently required for conventional copiers, e.g., xerographic copiers. Secondly, the circuitry employed in the image bar is all at high operating voltages. High voltages place limitations on the circuit elements that are employed and necessarily leads to increased costs. With the addition of switching elements necessary to supply high voltages to switching elements that supply high voltages to marking or writing elements, these circuit components, whether supplied as discrete components or as an integrated circuit as in Cowan et al, are costly to manufacture, bring about large amount of power dissipation and increase chance of high voltage shorting between circuit elements and present undesirable dangers to the safety of user personnel.
It is the primary objective of this invention to overcome these drawbacks concerning high illumination and voltage requirements in an image bar while applying present thin film or MOS/VLSI technology to provide a low cost and compact integrated image bar having an integral image reading and writing section for respectively reading an original document and immediately creating an image of the document.